The reaction of Mo 2(O 2CCH 3) 4 with 2-mercaptopyrimidine gave a green solid which was transformed by dissolving in pyridine in air to a red-orange crystalline product which has been shown by X-ray crystallography to be [MoO(NC 5H 5)(SN 2C 4H 3)] 2(μ-O) 2. The molecule has the familiar oxo-bridged dinuclear structure with the MoO bonds cisoid and distorted octahedra completed about each metal atom by a pyridine nitrogen atom, a pyrimidine nitrogen atom and the pyrimidine sulfur atom. No crystallographic symmetry is imposed but the molecule closely approximates C 2 symmetry. The MoMo distance is 2.576(1)Å. The crystallographic parameters are: Space group, P 1 ; a = 12.063(7)Å; b = 12.149(5)Å; c = 10.362(5)Å; α = 98.51(3)°; β = 104.84(4)°; γ = 102.91(4)°; V = 1396(1)Å 3; Z = 2. Using 3389 data with F o 2 >; 3σ(F o 2) and 313 variables, the structure was refined bu full-matrix least squares to final discrepancy indices of R 1 = 0.044 and R 2 = 0.073.